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31 Cards in this Set
- Front
- Back
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What is the delayed type hypersensitivity reaction seen in a previously exposed person to TB an example of?
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CD4+ Tcells responding to the protein challenge, with 2-3 days later a subsequent inflammatory reaction to get rid of it.
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How do Thelper cells induce an inflammatory reaction?
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By activating macrophages with IFN-y and CD40L/CD40 binding.
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When you inject a PPD of TB, what is the first step?
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Macrophages ingest the protein and display it on MHCII.
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What is this immune response called?
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The initial, innate response.
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What cells respond to this MHCII presentation of peptide?
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Thelper 1 cells
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What happens to the Th1 cells upon recognition of the antigen?
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-Upregulation of CD40L
-IFN-y secretion |
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What is the purpose of IFN-y secretion and CD40L expression?
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To further activate the macrophages that presented the Ag in the first place.
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Why would you want to activate macrophages?
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Because they can kill the microbes being presented if their ROI/NO generating mechanisms are ramped up.
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What do activated macrophages secrete?
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-TNF, IL-1, chemokines, and IL-12.
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What are the functions of TNF and IL-1?
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To increase the affinity and expression of CAMs on endothelial cells and T cells.
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What majorly important molecules are upregulated and expressed on APCs in response to IFN-y and CD40/CD40L binding?
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B7 - the costimulatory molecule.
MHC |
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What is the function of the IL-12 secreted by activated macrophages?
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It induces more naive CD4+ cells to differentiate into Th1 cells; creates a positive feedback loop as these then activate more APCs via IFN-y, they secrete more IL-12, and on and on.
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So what dangerous potential is there in the TH1 inflammatory reponse?
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It could become chronic if the stimulus antigen is not removed.
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So list 4 categories of things turned on in activated macrophages:
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1. NO/ROI's
2. TNF, Il-1, Il-12, chemokines 3. B7 4. MHC I and II |
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What happens to macrophage secretions once the pathogen is eliminated?
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It starts to release cytokines and growth factors like PDGF to start healing.
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What causes Th cells to differentiate into Th2 cells?
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IL-4
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What is the source of IL-4?
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Unknown
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What do Th2 cells secrete?
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-IL4, IL5, and IL10
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What do Th2 cytokines do?
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-Inhibit macrophage activation
-Causes class switching of plasma cells to IgE -Activates Eosinophils to aid in mast cell response |
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What pathogens are CD8 CTLs directed against?
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-Intracellular in cytoplasm
-Those that escape phagolysosomes |
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Do CTL effector cells require costimulatory signals?
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No
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What does CTL activation lead to?
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-Perforin release
-Granzyme release |
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What surface marker on CTLs allows them to kill infected cells without perforin/granzyme release?
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Fas-Ligand
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What cells express Fas receptor?
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Host cells infected with virus
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What are the 2 ways by which NAIVE CD8 Tcells are activated?
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1. Direct
2. Indirect |
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What is the direct way to activate naieve CD8 Tcells?
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1. MHC Class I presents Antigen
2. Costimulatory signal -Activates, proliferates via IL2, and differentiates into CTL. |
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What is the Indirect way to activate naive CD8 Tcells?
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1. APC presents antigen on MHCI
2. not enough costimulatory sig Thelper cells helps by activating the APC (CD40/CD40L upregulates B7 expression) |
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What is the indirect activation of naive Tcells an example of?
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CD4-CD8 cooperation
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If the APC doesn't express enough B7 to stimulate the CD8 cell, how can it stimulate the CD4 cell?
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i dont know
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Do CTLs get killed along with the target cells, when they release perforin and granzymes?
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No; they release and stay at the infection site to kill other target cells.
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How do granzymes kill the target cells exactly?
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By activating caspases which induce apoptosis.
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